Micellization and Mobility of Amphiphilic Poly(2-oxazoline) Based Block Copolymers Characterized by 1H NMR Spectroscopy

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• 作者：Wolf Hiller ; Nadine Engelhardt ; Anne-Larissa Kampmann ; Patrick Degen ; Ralf Weberskirch
• 刊名：Macromolecules
• 出版年：2015
• 出版时间：June 23, 2015
• 年：2015
• 卷：48
• 期：12
• 页码：4032-4045
• 全文大小：703K
• ISSN：1520-5835

文摘

Three amphiphilic diblock poly(2-oxazoline) copolymers composed of the hydrophilic poly(2-methyl-2-oxazoline) and hydrophobic poly(2-alkyl-2-oxazoline) with alkyl = pentyl (P1), heptyl (P2), and nonyl side chain (P3) lengths of the hydrophobic block were synthesized by ring-opening cationic polymerization. These polymers form micelles in water above their critical micelle concentration. The temperature-dependent stability of the micellar aggregates was analyzed by DLS and turbidity measurements as well as pyrene solubilization between 20 and 80 掳C in water. Moreover, the chemical composition of the block copolymers was determined by ¹H NMR spectroscopy. In particular, it was possible to quantify the degree of aggregations of the individual groups of both blocks by including the chemical composition into the derived equations. It could be shown by varying the temperature that both the chemical composition and the degree of micellization depend on the number of bonds of the considered structural groups of the side chain with respect to the backbone of the hydrophobic block as well as the length of the side chain. In addition, temperature-dependent T₁ and T₂ measurements were performed to determine the dynamics of the structural groups of the hydrophilic and hydrophobic blocks. Correlation times and activation energies were determined of the individual structural groups confirming the different mobilities.